User Guide to Thresholds and Classification - Environmental ...

182User Guide for Thresholds and Classificationsa. ≥ 1, but < 3, for corneal opacity, where the effects reverse within 21 days after exposure to thesubstance; orb. ≥ 1, but < 1.5, for iritis, where the effects reverse within 21 days after exposure to the substance; orc. ≥ 2, for conjunctival redness, where the effects reverse within 21 days after exposure to thesubstance; ord. ≥ 2, for conjunctival oedema (chemosis), where the effects reverse within 21 days after exposure tothe substance.The classification criteria above are based on the Globally Harmonised System for Classification andLabelling of Chemicals (GHS) (United Nations, 2007). See Appendix 12C for a comparison of the HSNO Actcriteria with the GHS criteria and Appendix 12D for comparisons with the EU risk phrases of effects on eyes.See Table 12.6 in Appendix 12B for an example of calculating a mean Draize score from an acute eyeirritation study.Substances mildly irritating to the eyeThe Globally Harmonized System of Classification and Labelling of Chemicals (GHS) (United Nations, 2007)acknowledges that substances classified as irritating to the eye may be only mildly irritating when the effectis fully reversible within 7 days. The Hazardous Substances and New Organisms Act 1996 (HSNO Act)classification system does not specifically mention this. However, this is a lesser degree of hazard.Therefore, a substance whose irritating effect fully reverses within 7 days is classified as category 6.4A, butthe identification of this hazard may state ‗mildly irritating to the eye‘ as opposed to ‗irritating to the eye‘.12.3. Classification of mixtures12.3.1. Classification of mixtures when data are available for the complete mixtureThe mixture will be classified using the criteria in sections 12.2.1 and 12.2.2, and taking into account thetesting and evaluation strategies used to develop data for these hazard classes.Unlike other hazard classes, alternative tests are available for skin corrosivity of certain types of chemicalsthat can give an accurate result for classification purposes, as well as being simple and relativelyinexpensive to perform. When considering testing the mixture manufacturers are encouraged to use a tieredweight-of-evidence strategy as included in the criteria for classification of substances for skin corrosion, eyecorrosion, and eye irritation to help ensure an accurate classification, as well as to avoid unnecessary animaltesting.A mixture is considered to cause eye corrosion (category 8.3A) if it has a pH of 2 or less or 11.5 or greater. Ifconsideration of the alkali/acid reserve suggests the substance or preparation may not have the potential tocause eye corrosion despite the low or high pH value, then further testing needs to be carried out to confirmthis, preferably by using an appropriate validated in vitro test.January 2012 EPA0109